The invention concerns an object of value, for example a credit card, a banknote or an identity card, comprising a carrier layer, for example a paper carrier, and at least one optical security element which is disposed on the carrier layer and which has a first layer containing a moiré pattern.
Moiré effects occur in a large number of natural and artificial structures. In addition the use of moiré structures as a security element in the area of production and use of banknotes is known.
Thus for example EP 0 930 979 B1 describes a banknote having two mutually spaced transparent windows. A first transparent window which is substantially free from an identification character includes a first moiré-inducing pattern comprising a set of closely spaced fine lines. A second transparent and substantially identification-free region of the banknote contains a second moiré-inducing pattern which also comprises a set of closely spaced fine lines. The fine lines of the first moiré-inducing pattern are arranged in substantially mutually parallel relationship in a transverse direction transversely across the banknote. The fine lines of the second moiré-inducing pattern extend in substantially mutually parallel relationship in the direction of the longitudinal axis. If the banknote is folded over itself along a predetermined fold line, then the first and the second regions are brought into alignment and in that way the moiré-inducing patterns of those regions are superimposed. Upon viewing in transmitting light, with such a superimposition, it is possible to see a series of dark bands which extend diagonally on the folded banknote and which are also known as Talbot stripes.
The second moiré-inducing pattern is accordingly used as an analyser for demonstrating the latent moiré image contained in the first moiré-inducing pattern.